Device for controlling the recycle of exhaust gas in an internal combustion engine

ABSTRACT

An internal combustion engine is disclosed in which a part of the exhaust gas is recycled to the upstream side of the throttle valve of the carburetor through an exhaust gas recycling device. The temperature near the throttle valve is monitored and a stop valve on the exhaust gas recycling device is closed when there is a danger that the water-content in the recycled exhaust gas might freeze.

United States Patent [191 Nohira Oct. 28, 1975 [54] DEVICE FOR CONTROLLING THE RECYCLE OF EXHAUST GAS IN AN INTERNAL COMBUSTION ENGINE [75] Inventor:

[73] Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha, Toyota, Japan 22 Filed: Feb. 22, 1974 21 Appl. No.: 445,292

'Hidetaka Nohira, Susono, Japan [30] Foreign Application Priority Data May 7, 1973 Japan 48-49792 [52] US. Cl. 123/119 A; 123/119 A [51] Int. Cl. F02M 25/06 [58] Field of Search 123/119 A; 261/DIG. 20, 261/129, 130

[56] References Cited UNITED STATES PATENTS 2,287,593 6/1942 Ball 123/119 A 2,414,296 1/1947 Gill 26l/DIG. 20 2,464,047 3/1949 Larkin 261/DIG. 2O

2,658,734 11/1953 Henning 261/D1G. 20 3,210,058 10/1965 Colvin 261/129 3,242,473 3/1966 Shivers, Jr. et a]. 261/DIG. 20 3,512,509 5/1970 Daigh 123/119 A 3,646,764 3/1972 Nakajima et a1..." 123/119 A 3,783,847 l/1974 Kolody 123/119 A 3,800,764 4/1974 Goto et 81.... 123/119 A 3,805,752 4/1974 Cataldo 123/119 A 3,817,232 6/1974 Nakajima et al 123/119 A Primary Examiner-Wendell E. Burns Assistant Examiner-David D. Reynolds Attorney, Agent, or FirmStevens, Davis, Miller & Mosher [5 7 ABSTRACT An internal combustion engine is disclosed in which a part of the exhaust gas is recycled to the upstream side of the throttle valve of the carburetor through an exhaust gas recycling device. The temperature near the throttle valve is monitored and a stop valve on the exhaust gas recycling device is closed when there is a danger that the water-content in the recycled exhaust gas might freeze.

2 Claims, 3 Drawing Figures US. Patent Oct. 28, 1975 FIG.

(c) TEMPERATURE OF ATMOSPHERE MEDPXE m0 mmpwqmmaimP 11 COOLER /5 FIG. 2

DEVICE FOR CONTROLLING THE RECYCLE OF EXHAUST GAS IN AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an internal combustion engine provided with an exhaust gas recycling means for use with such as an automobile and more particularly to an internal combustion engine in which the watercontent of the exhaust gas recycled is prevented from freezing within the carburetor.

2. Description of the Prior Art In the prior art, exhaust gas recycling devices for decreasing the NOx contained in the exhaust gas, it has been proposed to inject a part of the exhaust gas into the upstream side of the throttle valve of the carburetor with a view to facilitate the flow control. According to this method, however, the recycled exhaust gas passes through the throttle valve along with the fuel mixture and thus there arises the disadvantage that depending on various weather conditions, driving conditions, etc., the carburetor may become so cool that the water vapor, contained to about in the exhaust gas, may freeze either on the throttle valve or between the shaft bearings of the throttle valve, resulting in a misoperation of the throttle valve.

SUMMARY OF THE INVENTION It is an object of the invention to avoid that problem by stopping the recyling of the exhaust gas when there is the danger of the possible freezing of the watercontent in the exhaust gas due to the low temperature about the throttle valve of the carburetor.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a chart concerning the freezing condition for the water-content in the exhaust gas;

FIG. 2 is a system diagram showing an embodiment of the invention; and

FIG. 3 is a cross-section of another example for mounting the temperature sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENT It can be seen from FIG. 1 that freezing takes place when the ambient temperature comes below 0C for the case of drawing cool air as shown by the curve a and it as well takes place when the ambient temperature falls below *25C for the case of drawing warm air through the hot air cleaner as shown by the curve b. Thus the critical temperature within the carburetor at which freezing occurs is dependent on the suction air temperature as well as on the ambient weather condition and it is therefore possible to use the carburetor temperature to stop the recycling of the exhaust gas in order to prevent freezing.

An embodiment based on the idea mentioned above is shown in FIG. 2, in which an internal combustion engine comprising, as is well known, an air cleaner 1, a carburetor 2, a suction tube 8 on an engine body 7 and an exhaust tube 9, has a conduit 4 for recycling exhaust gas connected to a portion between the exhausttube 9 and an injection hole 3 provided in the upstream side of the throttle valve 6 of the carburetor, whereby a part of the exhaust gas is recycled from the exhaust tube to the carburetor under the constant pressure on the upstream side of the throttle valve during the engine operation. On the conduit 4 there are provided a cooler 5 for cooling the exhaust gas and an on-off valve 10.

The on-off valve 10 comprises a valve seat 11, valve body 12, a diaphragm 13 connected with the valve body 12 on the operating side, a spring 14 provided on the operating side of the diaphragm l3 and a diaphragm chamber 15. Upon introduction of manifold vacuum into the diaphragm chamber 15, the diaphragm 13 is bent upward against the spring 14 to move the valve body 12 away from the valve seat 11 to thereby open the conduit 4. In the absence of the manifold vacuum, the diaphragm 13 is reset by the spring 14 to bring the valve body 12 into contact with the valve seat 11 which shuts off the conduit 4.

The diaphragm chamber 15 of the on-off valve 10 is connected to a magnetic transfer valve 20 by means of pipe 16 which transmits the manifold vacuum. The magnetic transfer valve 20 comprises an outlet port 21 connected with the pipe 16, an inlet port connected by conduit 22 to intake manifold 8, a port 24 open to the ambient air, a valve body 25 which opens either the inlet port or ambient air port 24 when it closes the other, a spring 26 and a coil .27 for operating the valve body 25. When an electrical signal is delivered to the coil 27, the valve body 25 closes the ambient air port 24 and connects the inlet port attached to line 22 and the outlet port 21 so that the diaphragm chamber 15 will be supplied with manifold vacuum. When the electrical signal is absent, the spring 26 causes the valve body 25 to close the manifold vacuum inlet port and thus connects the ambient air port 24 and outlet port 21 so that the diaphragm chamber 15 is restored to atmospheric pressure.

A temperature sensor 16 is embedded in the carburetor 2 near its throttle valve 6 for detecting the temperature about the throttle valve. The temperature sensor 17 is electrically connected to the coil 27 of the magnetic transfer valve 20 via a controller 18 which deter mines whether a freezing condition is present in the interior of the carburetor. It is to be noted that the temperature sensor may comprise a thermistor using electrical resistance variation, a thermoswitch using a material property variation, etc., and it may be built into the valve shaft 6 of the throttle valve 6, as shown in FIG. 3.

With the arrangement described above, under normal weather conditions, the controller 18 generates an electric signal in response to the inner temperature of the carburetor sensed by the temperature sensor 17, so that the magnetic transfer valve 20 acts to supply manifold vacuum to the diaphragm chamber 15 to open the on-off valve 10 thereby recycling a part of the exhaust gas to the carburetor 2. When conditions exist such that there is a danger that the water-content in the exhaust gas will freeze within the carburetor, the controller 18 no longer generates an electric signal. This causes the magnetic transfer valve 20 to restore atmsopheric pressure in the diaphragm chamber 15 which closes the on-off valve 10 to thereby stop the recycling of the exhaust gas and as a result, freezing is prevented.

Thus it is understood that in accordance with the invention the recycling of exhaust gas can be stopped to prevent the freezing of the moisture contained in the exhaust gas whenever freezing is likely to take place, so that the throttle valve is always maintained in a reliable condition for the driver. Since the presence or absence of the freezing condition is determined'from the temperature in the carburetor, it is possible to obtain a reliable operation and a simplified construction for the controller.

Furthermore, through the use of the control system described above, it is also possible to prevent the overconcentration of thegas mixture which might occur when the temperature of the carburetor becomes abnormally high.

What is claimed is:

I. An internal combustion engine exhaust gas recycle control device comprising a conduit for recycling exhaust gas connected from the exhaust tube of the engine to the upstream side of the throttle valve of the carburetor, a cooler provided on said conduit, an onsaid carburetor, and an electro-magnetic transfer valve responsive to a signal from said controller for feeding said on-off valve with a pneumatic signal to close the on-off valve whenever there is the danger of freezing.

2. A device according to claim 1 wherein said temperature sensor is positioned within the valve shaft of the throttle valve. 

1. An internal combustion engine exhaust gas recycle control device comprising a conduit for recycling exhaust gas connected from the exhaust tube of the engine to the upstream side of the throttle valve of the carburetor, a cooler provided on said conduit, an on-off valve provided on said conduit, a temperature sensor provided in the carburetor near said throttle valve for detecting the temperature of the interior of the carburetor, a controller receiving a signal from said temperature sensor for determining whether or not the watercontent in the recycled exhaust gas will freeze within said carburetor, and an electromagnetic transfer valve responsive to a signal from said controller for feeding said on-off valve with a pneumatic signal to close the on-off valve whenever there is the danger of freezing.
 2. A device according to claim 1 wherein said temperature sensor is positioned within the valve shaft of the throttle valve. 